Paleomagnetic evaluation of the Yucca-Frenchman Flexure, southern Nevada
The eastern margin of the Yucca Flat basin, southern Nevada, is bounded by north-northwest-striking tilted fault blocks of the Halfpint Range that curve as much as 90{degrees} clockwise into east-northeast strikes in the French Peak-Massachusetts Mountain (FPMM) area. This pattern of arcuate structures was termed the Yucca Frenchman flexure by previous workers who attributed the arcuate pattern to clockwise drag along a proposed northwest-trending, right-lateral shear zone. The flexure model implies that rocks within the FPMM area have been rotated strongly clockwise about a vertical axis. Paleomagnetic data indicate no systematic vertical-axis rotation in the FPMM area and disprove the flexure model. After tilt correction, declinations of 30 site means obtained from the three ash-flow sheets in the FPMM area are more dispersed, but not systematically different than declinations of 12 site means from the Halfpint Range or declinations of 10 site means from little deformed reference areas to the west (Rainier and Pahute Mesas, Shoshone and northern Yucca Mountains). Paleomagnetic data indicate that structures in the FPMM area initiated with arcuate trends; not as originally straight elements that were rotated by right-lateral drag. The structures must have formed under the influence of locally different orientations and (or) ratios of principal stresses. The French Peak-Massachusetts Mountain area lies in an accommodation zone between domains of predominantly west- and east-tilted Miocene and Pliocene extensional fault blocks to the north and south, respectively. I suggest that local interaction between stress fields associated with fault zones that simultaneously propagated from north and south into the accommodation zone may have been responsible for the arcuate structures in the FPMM area.
- Research Organization:
- Geological Survey, Denver, CO (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AI08-86NV10583
- OSTI ID:
- 10109267
- Report Number(s):
- CONF-8909163--18; ON: DE92004278
- Country of Publication:
- United States
- Language:
- English
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Paleomagnetic evaluation of the Yucca-Frenchman flexure, southern Nevada
Paleomagnetic data bearing on the origin of arcuate structures in the French Peak--Massachusetts Mountain area of southern Nevada